Process of making nitric acid and other products.



FLS. WASHBURN.

PROCESS OFMAKlNG'NiTRIC ACID'AND OTHER PRODUCTS.

APPLICATION: FILED FEB. 7, I916.

Patented Nov. 28, 1916.

Frankki i shimrm 5y 4o much of the nitrose gases to enable a com- '-such gases, particularly ammonia, is very rBAnKs. WASHBU-RN, ornew yo nxfiv. Y.

To all whom it may concern: i Be it known that I, FRANK S. WASHBURN, a chemical engineer, and 'a' citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new anduseful A Improvements in Processes ofMaking Nitric Acid and other Products and I do hereby declare thefollowing to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertai is tomake and usetlie same.

This invention relatesfto a process of treating ammonia in such a manner as to pro:

duce ahighly concentrated nitric acid' simul' taneously with ammonia; salts, and has for itsobject to provideameansand-a method that will obviate the inherent-difliculties in the processes heretofore proposed, Whlle enabling one to operate more efficiently and economically. v

\Vith these and other objects in view, the invention consists in the apparatus as well as in the novel steps .aiidcombinations of steps,- constituting' the process, as will be more fully hereinafter disclosed and particularly pointedv out in 'the: claims.

In the well known processes of oxidizing ammonia it has long been recognized that when subjecting the ammonia and oxygen containing mixture to the influen :e of a suitable catalyzer, a simultaneous oxidation of the ammonia to nitrose gases and a decomposition of these nitrose gases to nitrogen gas takes place. Itis, therefore, will recognized that on'efmust so control these simultaneous reactions that the velocity of the oxidation reaction is very materially greaterthan the velocity of the decomposition reaction, for otherwise, one will decompose too inei'cially practicable process to result. In

one of the prioi processes the relative veloc- I ities of these two simultaneously occurring reactions are controlled by so adjusting the size of the catalyzing mass andthe velocity of thegases passing through it, that all the ammonia .is either oxidized or decomposed,

and none gets past in the form of free ammoniav But the, control of the velocity of complicated anddifficult, for it isinfluenced to a considerable extent by the relative quantities of ammonia and oxygen contained in the mixture-as well as by the actual rate at which the gas passes the catalyzer. In pracfrnoonss' o1" NITRIC 'AcID' AND o'rHEitPRoDucrs;

/ Application filed February 7, 1916. Serial IiTo. 76,647.,

tice' it is not only difiicult to maintain the desired uniform mixture containing the right proportions of ammonia and oxygen but even with a carefully designed catalyzer, it is almost impossible to pass every portion of this mixture at exactly the right rate Zuniformly, over every portion of the catalyzer,

so that no 'free ammonia escapes throiigh .without suffering a decomposition or an oxi- 5 dation. Accor dingly,this said prior process, on the average, has been forced to operate somewhat below its maximum rate, in order to avoid" obtaining free ammonia with the product. Further when operating'said prior proce'ss in practice, it is found that the decompos tion by the catalyzer ofthe" nitrose gases becomes quite serious and it is safe toassume that its efiicienfcy of oxidation of-the ammonia, is probably not over 7 5% to 85%. On the other hand, accordmg to theinvention now to be disclosed, it involves no serious inconvenience if the mixture containing ammonia and oxygen be passed at such a rate over or through the catalyzer that free ammonia appears in the products of the reaction; But one, of course,

should avoid passing said mixture at such a rate as to produce a very large excessof ammonia, for in that case other difliculties will result as will be now explained. That is to say, technlcal difliculties in designing and operating the oxidi-zing'apparatus prohibit the employment-of such a speed in. the mixture passing the catalyzer as will producea very largeexcess -of free ammonia on the exit side of the said catalyzer; but it is, yet commercially possible to employ such a speed through the catalyzer as will permit the production of large quantities'of nitrose gases, and some free ammonia, so that said nitrose gases may be converted into nitric acid-and said free ammonia may combine .with said acid to form ammonium nitrate, all as will more fully appear below. In

other words, should all the oxidized ammonia be thus converted into ammonium nitrate it will tend to condense in the colder portions of the apparatus, and clog them up so it is only by operating very skilfully in suchcases that one can practically carry out Specification of Letters Patent. Patented N v .28,' l

as I

the direct production of ammonium nitrate in this way. It is, however, very convenient to permit say 5% to 15% of the ammonia fed to the catalyzer to pass through undeno I composed, and it is with such relative smaller quantities of free ammonia, that I prefer to operate. In carrying out this invention I prefer to pass this free ammonia along with the nitrose gases through a suitable cooler and into an oxidation tower, when with a properlydesigned apparatus, a

-, very large proportion of that passing the means of any of the wall known sulfuric.

acid processes, converts this ammonium nitrate into ammonium sulfate and nitric acid, which acid can be recovered 'as such; and

when the sulfate has accumulated to a suit- 7 able concentration, itof itself, will precipitate out, and is recovered from the sulfuric acid in the usual and well known manner. As an alternativemethod I may so operate that I permit free ammonia to pass the catalyzer and form ammonium nitrate dissolved in nitric acid as above described and I then saturate the excess of nitric acid with ammonia from an outside source so as to produce from my oxidation apparatus ammonium nitrate as its sole product. This solution can be readily evaporated and crystallized, thus producing a dry ammonium nitrate which can be marketed as such, or

employed in many industries.

In case I do not desire to market the ammonium nitrate produced as above, I can treat the dry ammonium nitrate with a suitable concentration of sulfuric acid and convert all of it into ammonium sulfate and highly concentrated nitric, acid, which two products also find a ready market.

I have further found, when the velocity of my gas current, containing ammonia and oxygen, is increased, through, or over the catalyzer, to such a point that ammonia passes the catalyzer undecomposed, I am really obtaining a maximum velocity of the ammonia oxidation reaction, and aminimum velocity of the nitrose gas deomposition, referred to above; so'in such case, I obtain a very much higher efiiciency of oxidation of the ammonia with considerably less decomposition of either the ammonia or of the nitrose gases, than is the .case where I so limit the velocity of these gases through or over the catalyzer to such an extent that no ammonia appears in the products of the oxidation'as such. It therefore follows that by observing the quantity of free ammonia that passes the catalyzer, I am enabled to judge the real efficiency of the chemical reaction that is going on. In fact, it is a comparatively simple matter tooxidize ammonia by this system at an efiiciency far above 90%, if proper account is taken of the undec'omposed ammoniaIpassi'ngthe catalyzer. I I

In carrying out the process, I prefer to use a mixture of predetermined proportions ofammonia and oxygen, of ammonia air and oxygen or of ammonia and air, and to precool the same all in a manner similar to that disclosed in the copending application of Walter S. Landis, filed Feb. 15, 1915,

Serial No. 9595, and entitled Method of and apparatus for oxidizing ammonia.

In order that theinvention may be the more clearly understood, reference is had to the accompanying drawing forming a part of this specification, in which the figure is a diagrammatic partially sectional, par-' tially elevational view, of an apparatus suitable for carrying out the process.

Referring to the said drawing, 1 indicates any suitable conduit for supplying the ammonia'mixture to be oxidized, 2 a valved connection leading from said conduit to the oxidizing chamber 3. Located in the chamher 3 is any suitable form of cooler & adapt- I ed to cool the gaseous mixture before reaching the catalyzer 5, or to screen the oncoming stream of ammonia from the heat radiated from said catalyzer. The catalyzer may be of any suitable material, but I prefer iridium free platinum of a uniform cross section in order. that it may be uniformly heated by an electric current. After the gaseous mixture passes the catalyzer 5, it will be found to contain the oxids of nitrogen mixed with ammonia, water vapor and free nitrogen, if air was originally employed, and this mixture passes through the valved connections 6 to the conduit 7, thence preferably through a cooler 8, having a coil 9 and a supply 10 for a cooling medium.

.From the cooler S, the said mixture is conveniently p ssed through a suitable absorption tower 11 which may be supplied with water through the pipe 12, when the nitrose gases and free ammonia are readily taken up. A reaction now occurs by which there is formed a solution of nitric acid and ammonium nitrate which may be drawn off through the valved pipe 13 into the tank ll, and from this tank the said solution may be readily withdrawn through the valved connection 15 and valved connection 16. i

If the solution obtained in tank 1- is not sufficiently concentrated to warrant the separation of its nitrogen containing constituents, it may be repeatedly circulated through the tower 11 by means of the pump 18, pipe 19, tank 20 and valved connection 21, the unabsorbed gases in all cases escaping from tower 11, through the pipe 22. If the tower 11 is so designed as to absorb all the am monia and nitrose gases delivered to it, then the other gases contained in the mixture may be led to waste through said pipe 22.

But in those cases, where it-is less expensive to run the said nitrogen containing gases through a pluralityof towers, in order to absorb all the combinedinitrogen the said pipe 22 is led to one or more additional towers such as,25, from' which the waste gases escape through the pipe 26.

The tower 25 may be conveniently sup connection 30 to the tank 31, from which it'may be drawn ofi bymeans of the valved connections 32, and 16'when desired, or when said solution is found to be tooweak for drawing off it may be repeatedly circu-.

. lated back through said tower 25, by means of the pump 18, pipe 19, tank 20 and-connection 28. A valved pipe 35 permits the contents of the tank 31 to be emptied at will into the tank 14. When it is desired to convert all the nitric acid into ammonium nitrate free ammonia may be led to the' tower 11 through the valved pipe 40;

It is obvious that thos'e'skilled in the art may vary the details of both the process and apparatus without departing from the spirit of the invention, and therefore I do not wish to be limited 'to the above disclosure except as may be required. by the claims:

What I claim is 1. The process of oxidizing ammonia,

which consists in subjecting a suitable mixture ofgases containing ammonia and oxygen to .a suitable catalyzer and at such a velocity as to cause an oxid of nitrogen and free ammonia to appear in the products of the reaction, substantially as described.

2. The process of oxidizing ammonia which consists in spbjecting a mixture of ammonia. and oxygen .containin'ggases tothe action of a catalyzer at such a velocity that nitrose gases and undecomposed ammonia will appear in the ,products of the reaction; suitably combining said ammonia and nitrose gases; and s'eparatingout the ammonia compounds formed, substantially as described.

3. The process of producing nitric acid simultaneously with ammonium nltrate, which consists in sub1ect1ng a m xture of ammonia gas and oxygen containing gases in suitable proportions to the action of a catalyzer and at such a rate as to cause nitrose gases and not exceeding 20% of free ammonia to appear in the products; causing said gases and said-ammonia to chenncally combine 'to produce the said nitric acid and ammoniumn1trate; and separating these said nitrogen containing compounds, substantially as described. I

fl. The process of PIOdUClDg IlltI'lC acid and ammonium nitrate which conslsts 1n subjecting a mixture of ammonia and oxy- 'trating'said solution, substantially as described.

5. The process of producing nitric acid and ammonium nitrate, which consists'in subjecting a mixture of ammonia and oxyvgen. containing gases to'the act-ion of a catalyzer and at such a rate as to cause not exceeding 20% of free ammonia and nltrose gases to appear in the products of the reaction; producing a solution of nitric acid and ammonium nitrate from said products; concentrating said solution; and recovering the nitric acid remaining in said solution, substantially as described. -6. In an apparatus for oxidizing ammonia, the combination of an oxidizing chamber; a catalyzer in said chamber; a conduit for leading off the nitrogen compounds passing thecatalyzer; a cooler connected to said conduit; an absorption chamber connected to said cooler; means for passing free ammonia from an independent sourc to said absorption chamber a receptach into which the solutions from said -ab sorption chamber may be delivered; connections comprising a pump; and a second receptacle for returning said solutions to said chamber, substantially as described.

In testimony whereof I atfix my signature, in presence of two witnesses.

FRANK S. VASHBURN.

\Vitnesses:

G.. A. SCHURMAN E. J. PRANKE. 

